Door panel

ABSTRACT

The aperture area efficiency of a door panel with a double-panel structure having an outer panel and an inner panel is increased, while turbulent flow of air through ventilation holes is reduced. The outer panel  21  is provided with a plurality of honeycomb ventilation hole sections  26,  each of which comprises a plurality of hexagonal ventilation holes  25  that are formed in the outer panel  21  so as to be arranged in a honeycomb pattern, with each side of each ventilation hole  25  being adjacent to a side of another ventilation hole  25  with a connecting portion  25   a  therebetween. The inner panel  23  is provided with ventilation openings  30,  each of which is slightly larger than each respective honeycomb ventilation hole section  26  of the outer panel  21.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This is a U.S. national phase application under 35 U.S.C. §371 of International Patent Application No. PCT/JP2008/062165 filed Jul. 4, 2008 and claims the benefit of Japanese Application No. 2007-252537 filed Sep. 27, 2007. The International Application was published in the Japanese language on Apr. 2, 2009 as International Publication No. WO/2009/041141 under PCT Article 21(2). The contents of these applications are incorporated herein in their entirety.

TECHNICAL FIELD

The present invention relates to a door panel that is provided with an outer panel and an inner panel.

BACKGROUND OF THE INVENTION

FIG. 15 illustrates a hydraulic excavator 10, which is a work machine. The hydraulic excavator 10 includes a lower structure 11, an upper structure 12, a cab 13, a work equipment 14, and a power system 15 that includes an engine. The cab 13, the work equipment 14, and the power system 15 are mounted on the upper structure 12, which is rotatably mounted on the lower structure 11. The power system 15 is covered by a top cover 16, side doors 17,18, and other such components. The side doors 17,18 are mounted by hinges, which will be explained later, so as to be capable of opening and closing, and secured in the closed state by means of a latching device 19.

Such a side door of a work machine, which is opened and closed for maintenance of the engine room, the cooling package, etc., may be provided with a plurality of slot-like elongated air intake holes (e.g. See Japanese Laid-open Patent Publication No. 2006-170108 (page 7, and FIG. 2)). Other examples of such a side door include those provided with a plurality of louver slats (e.g. See Japanese Laid-open Patent Publication No. 10-213344 (page 2, and FIG. 9)).

Examples of conventional side doors also include a cover unit having a double-panel structure, with an inner panel conjointly affixed to an outer panel with a space provided therebetween. The inner panel has a plurality of recessed portions, and the outer panel and the inner panel are affixed to each other by bonding the recessed portions of the inner panel to the outer panel and hemming the peripheral edge of the outer panel (e.g. See Japanese Laid-open Patent Publication No. 9-228412 (page 2, and FIG. 8)).

In cases where a plurality of slot-like elongated air intake holes are formed in a side door of a work machine, it is necessary to provide partitions between the air intake holes. These partitions require a sufficient dimension to ensure the strength of the door, resulting in a reduced aperture area efficiency, which is the proportion of the area of the apertures to the opening region that extends from the air intake hole at one end to the air intake hole at the opposite end, as well as causing the air flow to be impaired by the partitions and increasing the possibility of turbulence at the partitions.

The louver slats also present a problem in that each louver slat requires a prescribed thickness due to concerns regarding strength, resulting in a reduced aperture area efficiency, as well as causing the air flow to be impaired by the louver slats and increasing the possibility of turbulence at the louver slats.

In cases where a cover unit having a double-panel structure is provided with air intake holes or ventilation openings to withstand severe heat, precise positioning of the ventilation openings that are formed in both the outer panel and the inner panel with respect to each other is usually required, making processing and assembly difficult.

In order to solve the above problems, an object of the invention is to increase the aperture area efficiency of a door panel with a double-panel structure having an outer panel and an inner panel, as well as reduce turbulence of air flow at the ventilation holes. Another object of the invention is to provide a door panel of which the outer panel and the inner panel can easily be positioned with respect to each other.

SUMMARY OF THE INVENTION

The present invention relates to a door panel provided with an outer panel and an inner panel that is formed so as to have an uneven surface with a recessed portion and a raised portion, with the recessed portion being affixed to the inner surface of the outer panel. The outer panel is provided with a honeycomb-shaped ventilation hole cluster formed of a plurality of hexagonal ventilation holes that are arranged in a honeycomb pattern, with each side of each respective ventilation hole being adjacent to a side of another ventilation hole with a connecting portion therebetween. The inner panel is provided with a ventilation opening that is formed in the recessed portion, at a location corresponding to the honeycomb-shaped ventilation hole cluster of the outer panel.

Further to the present invention, the ventilation opening of the inner panel of the door panel of the present invention is larger than the honeycomb-shaped ventilation hole cluster of the outer panel.

According to the present invention, for a door panel with a double-panel structure having an outer panel and an inner panel, by grouping ventilation holes so as to form densely arranged honeycomb-shaped apertures in the outer panel, a honeycomb-shaped ventilation hole cluster with a high aperture area efficiency can be formed at a location corresponding to the limited space of the ventilation opening in the inner panel. Furthermore, as the honeycomb-shaped ventilation hole cluster is formed by arranging a plurality of hexagonal ventilation holes in a honeycomb pattern so that each side of each respective ventilation hole is adjacent to a side of another ventilation hole with a connecting portion therebetween, it is possible to reduce fluid resistance by making the connecting portions between the ventilation holes narrow, while ensuring sufficient strength of these connecting portions. As a result, turbulent flow generated by obstruction of airflow by the connecting portions between the ventilation holes can be reduced.

Further to the present invention, the ventilation opening of the inner panel is larger than the honeycomb-shaped ventilation hole cluster of the outer panel and has sufficient clearance so that the inner panel is prevented from closing off the honeycomb-shaped ventilation hole cluster of the outer panel, even if the outer panel and the inner panel are not precisely positioned with respect to each other due to dimensional discrepancy resulting from shape tolerance of the press molded products. The configuration as above facilitates positioning of the outer panel and the inner panel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an enlarged perspective view of a door panel according to a first embodiment of the present invention.

FIG. 2 is an external view of the door panel.

FIG. 3 is a sectional view taken along the line III-III of FIG. 2.

FIG. 4 is a perspective view of the outer face of the door panel.

FIG. 5 is a perspective view of the inner face of the door panel.

FIG. 6 is an enlarged sectional view of the door panel.

FIG. 7 is a sectional view of a hemmed portion of the door panel.

FIG. 8 is an internal view of the hemmed portion of the door panel.

FIG. 9 is an exploded perspective view of the door panel.

FIG. 10 shows sectional views illustrating the mounting process of an internal reinforcing plate of the door panel, wherein (a) is a sectional view illustrating the internal reinforcing plate positioned in the inner panel and bonded thereto; (b) is a sectional view illustrating how the internal reinforcing plate and the inner panel are positioned in the area surrounded by the peripheral edge of the outer panel in the hemming process; and (c) is a sectional view illustrating how the internal reinforcing plate and the inner panel are immovably joined to the outer panel by hemming the outer panel.

FIG. 11 is a perspective view illustrating an adhesive retaining portion formed in the inner panel of the door panel.

FIG. 12 is a plan view of a work machine provided with the door panel.

FIG. 13 is an internal view of a door panel according to a second embodiment of the present invention.

FIG. 14 is a sectional view taken along the line XIV-XIV of FIG. 13.

FIG. 15 is a perspective view for schematically illustrating a work machine.

DETAILED DESCRIPTION OF THE INVENTION

Next, the present invention is explained in detail hereunder, referring to an embodiment shown in FIGS. 1 to 12, and another embodiment shown in FIGS. 13 and 14.

FIG. 12 illustrates a hydraulic excavator 10, which is a work machine. The hydraulic excavator 10 includes a lower structure 11, an upper structure 12, a cab 13, a work equipment 14, and a power system 15 that includes an engine. The cab 13, the work equipment 14, and the power system 15 are mounted on the upper structure 12, which is rotatably mounted on the lower structure 11. The power system 15 is covered by a top cover 16, side doors 17, and other such components. Each side door 17 is mounted by hinges, which will be explained later, so as to be capable of opening and closing, and maintained in the closed state by means of a latching device that will be explained later.

FIGS. 1 to 6 illustrate a door panel 20 of a side door 17. As illustrated in FIGS. 3 and 6, the door panel 20 includes an outer panel 21, an inner panel 23, and a foamed material 24. The inner panel 23 is formed by means of press molding so as to have an uneven surface with recessed portions and raised portions. The recessed portions are fixed to the inner surface of the outer panel 21, and a space 22 is formed between the raised portions and the inner surface of the outer panel 21 and filled with the aforementioned foamed material 24.

The outer panel 21 has a thickness ranging from 1.2 to 5.0 times that of the inner panel 23. In other words, an iron plate that is thinner than the outer panel 21 is used to form the inner panel 23. For example, if the outer panel 21 is an iron plate with a thickness of 1.2 mm, it is desirable to use a thin iron plate with a thickness of, for example, 0.6 or 0.8 mm to form the inner panel 23 in order to obtain sufficient strength and workability, which are reciprocal properties.

As illustrated in FIG. 6, the foamed material 24 is formed by heating an unactivated foaming sheet of a foaming material 24 a, which is attached to the inner surface of the inner panel 23, so that the heated foaming material 24 a is activated and expands inside the space 22 between the outer panel 21 and the inner panel 23. A highly expandable foaming rubber-base sound absorbing material that has an approximately 20-fold volumetric thermal expansion coefficient may desirably be used as the foaming material 24 a. It is desirable to conduct the heating of the foaming material 24 a during the baking finish process using a baking finish heating apparatus.

As illustrated in FIGS. 2 and 4, the outer panel 21 has a plurality of honeycomb ventilation hole sections 26 serving as ventilation hole clusters, each of which comprises a plurality of hexagonal ventilation holes 25 that are formed through the material of the outer panel 21 so as to be arranged in a honeycomb pattern, with each side of each respective ventilation hole 25 being adjacent to a side of another ventilation hole 25 with a connecting portion therebetween.

It is desirable that each ventilation hole 25 be formed in a regular hexagon, with each side being of equal length. However, a vertically or laterally elongated hexagon is also permissible, provided that the hexagon is vertically as well as laterally symmetrical.

As illustrated in FIGS. 1 and 5, the inner panel 23 has adhering portions 27,28, which are the aforementioned recessed portions joined to the inner surface of the outer panel 21, and a raised portion 29 bulging from the adhering portions 27,28.

As illustrated in FIG. 5, of the adhering portions 27 of the inner panel 23, those surrounded by the raised portion 29 comprise three laterally extending rows, which are provided at locations respectively corresponding to the rows of the honeycomb ventilation hole sections 26 of the outer panel 21. As illustrated in FIG. 1, each one of these laterally extending adhering portion 27 is provided with ventilation openings 30, each of which is larger than each honeycomb ventilation hole section 26 of the outer panel 21.

To be more specific, a plurality of ventilation openings 30 are formed in the adhering portions 27 that are surrounded by the raised portion 29 and serve as a part of the recessed portions of the inner panel 23. Each ventilation opening 30 corresponds to and is slightly larger than each respective honeycomb ventilation hole section 26 of the outer panel 21.

As illustrated in FIGS. 7 to 8, the peripheral edge 31 of the outer panel 21 is hemmed by folding the peripheral edge 31 of the outer panel 21 so as to curl over the peripheral edge 32 of the inner panel 23 and then pressing down the folded part. In other words, the outer panel 21 has a hemmed portion 33 that is formed by folding the peripheral edge 31 of the outer panel 21 so as to curl over the peripheral edge 32 of the inner panel 23 and then pressing down the folded part substantially flat so that the peripheral edge 31 of the outer panel 21 interlockingly secures the peripheral edge 32 of the inner panel 23.

As illustrated in FIG. 7, at least the peripheral edge 32 of the inner panel 23 is bonded to the outer panel 21 with an adhesive 34, which joins as well as seals the outer panel 21 and the inner panel 23 together at the hemmed portion 33. The adhesive 34 may desirably be a paste-type structural adhesive having both viscous and thermosetting properties.

As illustrated in FIGS. 1 and 8, the peripheral edge 31 of the outer panel 21 is provided with corner notches 35 and intermittent folded portion notches 36, each of which is formed by partially cutting away the folded part of a corner or an intermittent folded portion of the peripheral edge 31, respectively. The corner portions of the inner panel 23 that correspond to the corner notches 35 of the outer panel 21 are rounded.

FIG. 9 is an exploded perspective view of the side door 17, illustrating how an internal reinforcing plate 41 for mounting hinges is affixed. To be more specific, the internal reinforcing plate 41 is sandwiched between the outer panel 21 and the inner panel 23 in the state where the inner panel 23 is positioned on and affixed to the inner surface of the outer panel 21.

The internal reinforcing plate 41 is provided at the middle portion thereof with a corrugated adhering portion 42 including alternating ridges and furrows. Hinge mounting surface portions 43,44 are respectively formed continuously with one end and the opposing end of the corrugated adhering portion 42. A positioning fitting portion 45 and a positioning fitting portion 46, both of which have a concave shape, are formed adjacent to the hinge mounting surface portions 43,44, respectively.

At the location corresponding to the internal reinforcing plate 41, the inner panel 23 is provided with a corrugated adhering portion 47 including alternating ridges and furrows. The corrugated adhering portion 47 is formed at the middle part of the hinge-attaching end of the raised portion 29 of the inner panel 23. Hinge mounting openings 48,49 are respectively formed adjacent to one end and the opposing end of the corrugated adhering portion 47. A positioning fitting portion 51 and a positioning fitting portion 52, both of which are in the shape of a protrusion protruding downward, are formed adjacent to the hinge mounting openings 48,49, respectively.

The two positioning fitting portions 45,46 of the internal reinforcing plate 41 have different dimensions, and, correspondingly, the positioning fitting portions 51,52 of the inner panel 23, too, have different dimensions. The positioning fitting portion 45 and the positioning fitting portion 51, which are respectively formed at mutually corresponding locations on the internal reinforcing plate 41 and the inner panel 23, fit to each other in a male-female engagement. The positioning fitting portion 46 and the positioning fitting portion 52, which are respectively formed at another pair of mutually corresponding locations on the internal reinforcing plate 41 and the inner panel 23, fit to each other in a male-female engagement.

When the internal reinforcing plate 41 is positioned on and fitted to the inner panel 23, the corrugated adhering portion 42 of the internal reinforcing plate 41 is brought into direct contact with the reverse surface of the corrugated adhering portion 47 of the inner panel 23, to which an adhesive is applied, and the hinge mounting surface portions 43,44 of the internal reinforcing plate 41 are aligned with the hinge mounting openings 48,49 of the inner panel 23 so that hinges 53,54 can be respectively welded to the hinge mounting surface portions 43,44 of the internal reinforcing plate 41 through the hinge mounting openings 48,49.

As illustrated in FIG. 9, mounting holes 55 a, 55 b for mounting a latching device are formed in the outer panel 21 and the inner panel 23, respectively.

FIG. 10 illustrates a method of producing the door panel 20 incorporating the internal reinforcing plate 41. The inner panel 23 includes the raised portion 29, which is the portion bulging away from the outer panel 21. As illustrated in FIG. 10( a), the internal reinforcing plate 41 is positioned inside the raised portion 29 of the inner panel 23 and bonded thereto by means of the adhesive applied to the corrugated adhering portions 42,47. The adhesive is the thermosetting adhesive 34 and also applied to the joint surfaces of the internal reinforcing plate 41 and the inner panel 23 to be joined to the outer panel 21. As illustrated in FIG. 10( b), in the state where the peripheral edge 31 of the outer panel 21 is folded but still open as the hemming process is not yet completed, and the adhesive has been applied to the inner panel 23, the inner panel 23 and the internal reinforcing plate 41 are positioned on the outer panel 21 by fitting the inner panel 23 in the area surrounded by the peripheral edge 31 of the outer panel 21 so that the internal reinforcing plate 41 is sandwiched between the outer panel 21 and the inner panel 23. Then, as illustrated in FIG. 10( c), the inner panel 23 and the internal reinforcing plate 41 are immovably joined to and sealed along the inner surface of the outer panel 21 by hemming the peripheral edge 31 of the outer panel 21 so that the peripheral edge 31 is folded while curling over the peripheral edge 32 of the inner panel 23.

As illustrated in FIG. 6, the inner panel 23 includes the raised portion 29 bulging from the recessed adhering portions 27, which are in direct contact with the outer panel 21. A reinforcing deformed portion 56 is formed in a step-like shape along the middle of each sloping side of the raised portion 29. The adhering portions 27 of the inner panel 23 are bonded to the outer panel 21 with the adhesive 34. The raised portion 29 has ascending portions 57, each of which has an arc-shaped cross section and continuously extends along the foot of the raised portion 29 rising from the corresponding adhering portion 27.

As illustrated in various drawings including FIGS. 1 and 5, the raised portion 29 and each reinforcing deformed portion 56 are formed in an endless manner along the recessed adhering portions 27.

As illustrated in FIG. 11, the adhering portions 27 of the inner panel 23, which are bonded to the outer panel 21 with the adhesive 34, are provided with adhesive retaining portions 68, each of which is formed in the shape of a continuously extended raised portion and includes an adhesive retaining channel 67 for retaining the adhesive 34. Each adhering portion 27 surrounded by the raised portion 29 includes vertically extending portions extending along the ventilation openings 30, which are formed at locations corresponding to the ventilation holes 25 of the outer panel 21. To be more specific, each vertically extending portion of the adhering portions 27 extends between a ventilation opening 30 and a ventilation opening 30 adjacent thereto, and the adhesive retaining portions 68 of the inner panel 23 are formed respectively in these vertically extending portions and extend along the ventilation openings 30.

As illustrated in FIG. 11, each ventilation opening 30 is slightly larger than each respective honeycomb ventilation hole section 26, in other words each region in which ventilation holes 25 are clustered, with a clearance portion 30 a between the peripheral edge of each ventilation opening 30 and the honeycomb ventilation hole section 26 therein so that the peripheral edge of each ventilation opening 30 does not overlap the corresponding ventilation holes 25 formed in the outer panel 21. Furthermore, it is desirable to form each connecting portion 25 a between each respective ventilation hole 25 and a ventilation hole 25 adjacent thereto as narrow as possible so as not to obstruct air flow through the ventilations holes 25, provided that the strength of the outer panel 21 is maintained.

As illustrated in FIG. 5, the raised portion 29 of the inner panel 23 is so formed as to bulge from the adhering portions 27,28. The raised portion 29 has reinforcing raised portions 29 a, each of which is a continuously extending raised portion. The reinforcing raised portions 29 a are provided at the vertical ends of the rows of ventilation openings 30 and extend along the laterally extending adhering portions 27, which are bonded to the outer panel 21. Furthermore, reinforcing indentations 70 are formed across the reinforcing raised portions 29 a.

Next, a production process of the door panel 20 is explained.

The foaming material 24 a is attached to the inner surface of the raised portion 29 of the inner panel 23 as illustrated in FIG. 6. As illustrated in FIG. 10( a), the internal reinforcing plate 41 for mounting hinges is joined to the reverse surface of the raised portion 29 of the inner panel 23, at a location in the proximity of one of the lateral ends of the inner panel 23, and the thermosetting adhesive 34, which is necessary for bonding the outer panel 21 thereto, is applied to the adhering portions 27, which serve as a part of the recessed portions of the inner panel 23, as well as to the internal reinforcing plate 41. As illustrated in FIG. 10( b), the outer panel 21 and the inner panel 23 are positioned and layered one on top of the other. As illustrated in FIG. 10( c), the inner panel 23 and the internal reinforcing plate 41 are joined to the inner surface of the outer panel 21 by hemming the peripheral edge 31 of the outer panel 21 so that the peripheral edge 31 is folded while curling over the peripheral edge 32 of the inner panel 23 and the folded parts are pressed down substantially flat.

Thereafter, the inner panel 23 and the internal reinforcing plate 41 are bonded to the outer panel 21 by heating the adhesive 34 using the baking finish heating apparatus to harden the adhesive 34. Then, as illustrated in FIG. 6, the foaming material 24 a is expanded to fill the space 22 with the foamed material 24 by heating using the baking finish heating apparatus. Furthermore, the paint that has been sprayed beforehand onto the outer surface of the outer and inner panels 21,23 is baked thereon by heating using the baking finish heating apparatus.

For example, thermal hardening of the adhesive 34 is conducted by heating for 5 minutes at 150° C.; formation of the foamed material 24 by expansion by heating for 20 minutes at 150° C.; and baking finish by heating for 20 minutes at 180° C. to 200° C. Such heating can be performed by using a conventional baking finish heating apparatus.

Finally, as illustrated in FIG. 5, hinges 53,54 are respectively welded to the hinge mounting surface portions 43,44 of the internal reinforcing plate 41 through the hinge mounting openings 48,49 of the inner panel 23 by fillet welding or other appropriate method, and a latching device 19 is attached to the mounting holes 55 a of the outer panel 21 and the mounting holes 55 b of the inner panel 23.

Next, the functions and effects of the embodiment illustrated in FIGS. 1 to 12 are explained hereunder.

As illustrated in FIG. 6, the hollow structure with a closed cross section formed of the outer panel 21 and the inner panel 23, which is thinner than the outer panel 21, can make the entire door panel 20 lighter. Furthermore, as the closed cross section of this hollow structure has sufficient height, being formed of the inner panel 23 and the outer panel 21 with a thickness greater than that of the inner panel 23, i.e. 1.2 to 5.0 times thicker than the inner panel 23, the door panel has sufficient strength against an external impact. Therefore, this embodiment provides a door panel that is light in weight and has sufficient strength at inexpensive cost.

Furthermore, the foamed material 24 filling the space between the outer panel 21 and the inner panel 23 is capable of absorbing sound and thereby effectively damping sound generated from the door panel itself and, consequently, provides high damping effect to reduce noise.

As illustrated in FIGS. 1 and 5, the inner panel 23 includes recessed adhering portions 27 and a raised portion 29 bulging from the adhering portions 27. Therefore, because of the uneven surface structure formed of the adhering portions 27 and the raised portion 29, the inner panel 23 has increased rigidity and, consequently, increased strength, in spite of being thinner than the outer panel 21.

As illustrated in FIGS. 7 and 8, the hemmed portion is formed by folding the peripheral edge 31 of the outer panel 21 so as to curl over the peripheral edge 32 of the inner panel 23 and then pressing down the folded part. Therefore, even with the outer panel 21 that is thicker than the inner panel 23, the embodiment is capable of providing a hemmed portion 33 with a uniform shape, and thereby providing a folded joint portion having stable quality.

In other words, the hemmed portion 33, at which the peripheral edge of the outer panel 21 interlockingly secures the peripheral edge of the inner panel 23, is formed by folding the peripheral edge of the outer panel 21 so as to curl over the peripheral edge of the inner panel 23 and then pressing down the folded part flat. Therefore, compared with a conventional hemming in which the folded part of the outer panel 21 protrudes in a circular cross section, the hemmed portion 33 of the outer panel 21 results in a stable shape and ensures uniform quality.

In a hemming process, it is not easy to fold the peripheral edge of the outer panel 21 at a corner or an intermittent folded portion of the outer panel 21. According to the present embodiment, however, as illustrated in FIGS. 1 and 8, the outer panel 21 is provided with corner notches 35 and intermittent folded portion notches 36, each of which is formed by partially cutting away the folded part of a corner or an intermittent folded portion of the peripheral edge 31, respectively. Because of these notches, the peripheral edge 31 of the outer panel 21 can be folded and pressed down flat easily and precisely even at the corners and the intermittent folded portions of the outer panel 21.

As illustrated in FIG. 7, the outer panel 21 and the inner panel 23 can assuredly be conjoined by means of bonding with the adhesive 34 and the hemmed portion 33 of the outer panel 21. Furthermore, the adhesive 34 also provides effective sealing.

As illustrated in FIG. 8, the corner portions of the inner panel 23 that correspond to the corner notches 35 of the outer panel 21 are rounded so that the corner portions of the inner panel 23 are prevented from protruding from the corner notches 35 of the outer panel 21.

As illustrated in FIGS. 1 and 11, each ventilation opening 30 of the inner panel 23 is larger than each respective honeycomb ventilation hole section 26 of the outer panel 21. Therefore, when the inner panel 23 is conjoined with the inner surface of the outer panel 21, the inner panel 23 is prevented from closing off the honeycomb ventilation hole sections 26 of the outer panel 21 regardless of the dimensional tolerance arising from production of the outer panel 21 and the inner panel 23; in other words, even if the outer panel 21 and the inner panel 23 are not precisely positioned with respect to each other due to dimensional discrepancy resulting from shape tolerance of the press molded products, the honeycomb ventilation hole sections 26 of the outer panel 21 shift only within the range of the clearance portions 30 a of the respective ventilation openings 30. Therefore, by thus preventing interference with the ventilation aperture area of the outer panel 21 and the inner panel 23, this configuration ensures a prescribed aperture area, and, furthermore, facilitates positioning of the outer panel 21 and the inner panel 23, thereby increasing working efficiency in the manufacturing process.

Furthermore, as a result of the configuration described above, for a door panel with a double-panel structure having an outer panel 21 and an inner panel 23, by grouping ventilation holes 25 so as to form densely arranged honeycomb-shaped apertures in the outer panel 21, honeycomb ventilation hole sections 26 with a high aperture area efficiency can be formed at locations respectively corresponding to the limited spaces of the ventilation openings 30 in the inner panel 23. Furthermore, as each honeycomb ventilation hole section 26 is formed by arranging a plurality of hexagonal ventilation holes 25 in a honeycomb pattern so that each side of each respective ventilation hole 25 is adjacent to a side of another ventilation hole 25 with a connecting portion 25 a therebetween, it is possible to reduce fluid resistance by making the connecting portions 25 a between the ventilation holes 25 narrow, while ensuring sufficient strength of these connecting portions 25 a. As a result, compared with ventilation hole clusters that are formed of grouped circular or square holes, turbulent flow generated by obstruction of airflow by the connecting portions 25 a between the ventilation holes 25 can be reduced.

As illustrated in FIG. 5, the plurality of sets of honeycomb ventilation hole sections 26 and ventilation openings 30 ensures a sufficient aperture area for ventilation.

As illustrated in FIG. 9, as the internal reinforcing plate 41 provided in the raised portion 29, which is the portion of the inner panel 23 raised away from the outer panel 21, is secured between the inner panel 23 and the outer panel 21, the inner panel 23 is reinforced at the raised portion 29 by the internal reinforcing plate 41. A particular feature lies in that the internal reinforcing plate 41 is immovably positioned with respect to the inner panel 23 in a male-female engagement. Therefore, as merely fitting the internal reinforcing plate 41 to the inner panel 23 in a male-female engagement during the production process is sufficient to precisely control the position of the internal reinforcing plate 41, the internal reinforcing plate 41 can precisely be positioned and fixed to a location where reinforcement is most effective.

To be more specific, a male-female engagement of a pair of positioning fitting portions 45,51 and a male-female engagement of another pair of positioning fitting portions 46,52 enable the internal reinforcing plate 41, which has an elongated shape, to be easily and securely positioned to the inner panel 23.

The pair of positioning fitting portions 45,51 differs from the other pair of positioning fitting portions 46,52 in its dimensions. Therefore, should the internal reinforcing plate 41 be position in a wrong orientation, it is impossible to align the positioning fitting portions 45,46 of the internal reinforcing plate 41 with the positioning fitting portions 51,52 of the inner panel 23. This feature ensures the internal reinforcing plate 41, which has a prescribed orientation, to be properly installed in the inner panel 23.

As the hinges 53,54 are respectively welded to the hinge mounting surface portions 43,44 of the internal reinforcing plate 41 through the hinge mounting openings 48,49, which are formed in the inner panel 23, the hinges 53,54 are more solidly affixed, compared with cases where the hinges 53,54 are mounted on the inner panel 23.

As illustrated in FIG. 10, in the state where the peripheral edge 31 of the outer panel 21 is folded but still open as the hemming process is not yet completed, and the adhesive has been applied to the inner panel 23, the inner panel 23 and the internal reinforcing plate 41 are positioned on the outer panel 21 by fitting the inner panel 23 in the area surrounded by the peripheral edge 31 of the outer panel 21, with the internal reinforcing plate 41 sandwiched between the outer panel 21 and the inner panel 23. Then, the inner panel 23 and the internal reinforcing plate 41 are secured to the inner surface of the outer panel 21 by hemming the peripheral edge 31 of the outer panel 21 so that the peripheral edge 31 is folded while curling over the peripheral edge 32 of the inner panel 23. This configuration can provide a door panel production method that ensures, by means of the internal reinforcing plate 41, that the inner panel 23, which is formed in an uneven surface protruding away from and recessed towards the outer panel 21, has sufficient strength at its raised portion 29, while making effective use of the peripheral edge 31 of the outer panel 21 for positioning the inner panel 23 when the hemming process is not yet completed.

As illustrated in FIG. 6, the hollow structure with a closed cross section formed of the outer panel 21 and the inner panel 23 ensures sufficient strength. Furthermore, the inner panel 23 includes the raised portion 29 bulging from the adhering portions 27, which are in direct contact with the outer panel 21. A stepped reinforcing deformed portion 56 is formed along the middle of each sloping side of the raised portion 29. Therefore, the strength of the inner panel 23 is increased compared with an inner panel that is not provided with such a stepped portion 56, resulting in improvement of the strength of the entire door panel.

As illustrated in FIG. 5, the adhering portions 27, and the raised portion 29 and the reinforcing deformed portions 56, which are formed in an endless manner along the adhering portions 27, reinforce each other and thereby increase the strength of the entire inner panel 23.

As illustrated in FIG. 11, the adhering portions 27 of the inner panel 23, which are bonded to the outer panel 21 with the adhesive 34, are provided with adhesive retaining portions 68, each of which includes an adhesive retaining channel 67 for retaining the adhesive 34. When the inner panel 23 is pressed against the outer panel 21, the adhesive 34 forced out from between the outer panel 21 and the adhering portions 27 of the inner panel 23 remains in the adhesive retaining channels 67 of the adhesive retaining portions 68. Therefore, when the adhesive 34 hardens, the adhering strength of the adhesive 34 is maintained. Furthermore, in cases where the door panel 20 is used as a side door, the adhesive retaining portions 68, which extend vertically in the vertically extending portions of the adhering portions 27 that are surrounded by the raised portion 29, also serve as vertically extending columns and thereby increase the strength of the door panel 20 to withstand a vertical load.

As illustrated in FIG. 5, the inner panel 23 includes the adhering portions 27, which are bonded to the outer panel 21. The reinforcing raised portions 29 a, each of which is a continuously extending raised portion, extend along the adhering portions 27. While these reinforcing raised portions 29 a have a reinforcing function to increase the strength of the inner panel 23 bonded to the outer panel 21, the reinforcing indentations 70, which are indentations formed across the reinforcing raised portions 29 a, further enhance the reinforcing function of the reinforcing raised portions 29 a. In short, by providing the inner panel 23 with a complicated uneven shape with the reinforcing raised portions 29 a and the reinforcing indentations 70, which extend in a direction intersecting the direction in which the reinforcing raised portions 29 a extend, the inner panel 23 can be further reinforced.

Next, FIGS. 13 and 14 illustrate another embodiment of the present invention. In short, the embodiment relates to a door panel that does not have a stepped reinforcing deformed portion 56, which is provided in the case of the embodiment illustrated in FIGS. 1 to 12. As the other components and elements, including the structure wherein each ventilation opening 30 of the inner panel 23 is larger than each respective honeycomb ventilation hole section 26 of the outer panel 21, are similar to those of the embodiment illustrated in FIGS. 1 to 12, they are identified with the same reference numerals, and their explanation is omitted herein.

The present invention is applicable to a door panel of a work machine, such as a hydraulic excavator illustrated in FIG. 12 or FIG. 15. 

1. A door panel comprising: an outer panel; and an inner panel formed having an uneven surface with a recessed portion and a raised portion, the recessed portion affixed to the inner surface of the outer panel, wherein: the outer panel with includes a honeycomb-shaped ventilation hole cluster formed of a plurality of hexagonal ventilation holes that are arranged in a honeycomb pattern, with each side of each respective ventilation hole being adjacent to a side of another ventilation hole with a connecting portion therebetween; and the inner panel includes a ventilation opening that is formed in the recessed portion, at a locations corresponding to the honeycomb-shaped ventilation hole cluster of the outer panel.
 2. A door panel as claimed in claim 1, wherein: the ventilation opening of the inner panel is larger than the honeycomb-shaped ventilation hole cluster of the outer panel. 